The number of infectious illness outbreaks on cruise ships
has dropped sharply in the last 12 months, greatly extending what had already
been a stretch of smooth sailing for the industry.
Since July 2016, just four ships have experienced
gastrointestinal illness that reached the level of an outbreak, according to
the U.S. Centers for Disease Control (CDC), which monitors cruise ship
That compares with an average of 19 outbreaks annually from
2008 to 2014.
About 70% of the gastrointestinal outbreaks are caused by
norovirus, a common malady that lasts for several days, is easily transmitted
and comes aboard cruise ships with passengers who are already sick.
The virus causes outbreaks in many places where people
congregate on land, such as schools and nursing homes, but only cruise lines
have agreed to report the outbreaks to federal health authorities.
Last year, there were 13 episodes of illness on cruise
ships, according to the CDC's website, but only two after mid-year. They
occurred on the P&O Cruises ship Adonia, which was sailing for Carnival
Corp.'s Fathom brand at the time, and on Holland America Line's Oosterdam.
This year, outbreaks have been reported only on Princess
Cruises' Coral Princess, in March, and Oceania's Regatta, in April.
LaKia Bryant, a spokeswoman for the CDC, said the rate of
gastrointestinal illness on cruise ships has decreased over time "as has
the number and severity of outbreaks by year, except 2012, when a new strain of
Still, if the outbreaks continue at their current pace, 2017
will have by far the lowest number on record.
Bryant said that the trend is likely the result of several
One is earlier detection of illness. Cruise lines have been
refining their response to viral outbreaks for more than a decade and are
becoming better practiced at identifying sick passengers and quarantining them
before an outbreak can get started.
One line that has a particularly good track record is
Carnival Cruise Line, which has only had one outbreak in the past six years.
Jennifer De La Cruz, vice president of communications at
Carnival, said that over the past 10 years, "We have typically had either
zero or one outbreak per year. We credit that to very close monitoring,
tracking and rapid implementation of outbreak-prevention protocols if we start
to see any unusual uptick in number of [gastrointestinal] cases."
Another factor, Bryant said, is cruise industry diligence in
"developing and implementing ... outbreak prevention and control plans."
Cruise lines have adopted a number of measures to prevent
outbreaks. At Holland America Line, for example, passengers are asked not to
serve themselves at the buffet restaurant in the first few days of the cruise,
but instead allow crew to handle the food.
Most newly built cruise ships for the past couple of years
have included hand washing stations at the entrance to the buffet.
Bryant said such innovations were part of the industry "proactively
looking for ways to use the most current science and limit the spread" of
The long-term decline in outbreaks at sea was documented in
a January 2016 paper in the CDC publication Morbidity and Mortality Weekly
Three health researchers affiliated with the CDC found that
from 2008 to 2014, rates of acute gastroenteritis per 100,000 travel days
decreased among cruise passengers, from 27.2 cases in 2008 to 22.3 in 2014.
The rates were lower than in a similar study of the
Researchers found that of the 29,107 voyages during the
period, 133 (0.5%) had reported an outbreak, and of those outbreaks where
testing enabled verification, 92% were caused by norovirus.
The report went on to say that the seasonality of norovirus
outbreaks is the same onboard ships as it is on land, with higher rates of
illness reported during the November--through-April period each year.
This past winter, there were norovirus outbreaks reported by
local health authorities in several California school districts, including one
that infected at least 700 elementary and middle school students in Ventura
County, north of Los Angeles.
The CDC said its collaboration with the cruise industry
helps support efforts to contain outbreaks and spread knowledge about effective
countermeasures. Individual cruise companies also share best practices.
Carnival Corp. chief communications officer Roger Frizzell
said the company's brands share their own best practices, especially in the
areas of health, environment, safety and security. He said that former Navy
vice admiral Bill Burke, who joined Carnival several years ago as chief
maritime officer, has focused on illness prevention, "and it is having an
"The cruise industry as a whole has always done a great
job in this area," Frizzell said. "In fact, the data shows the best
way not to attract norovirus is to take a cruise."